Fistulae occur commonly in man. Such fistulae may be congenital or may be caused by infection, inflammatory bowel disease (Crohn's disease), irradiation, trauma, childbirth, or surgery, for example.
Some fistulae occur between the vagina and the bladder (vesico-vaginal fistulae) or between the vagina and the urethra (urethro-vaginal fistulae). These fistulae may be caused by trauma during childbirth. Traditional surgery for these types of fistulae is complex and not very successful.
Other fistulae include, but are not limited to, tracheo-esophageal fistulae, gastro-cutaneous fistulae, and anorectal fistulae. For example, anorectal fistulae may occur between the anorectum and vagina (recto-vaginal fistulae), between the anorectum and bladder (recto-vesical fistulae), between the anorectum and urethra (recto-urethral fistulae), or between the anorectum and prostate (recto-prostatic fistulae). Anorectal fistulae may result from infection in the anal glands, which are located around the circumference of the distal anal canal forming an anatomic landmark known as the dentate line 1, shown in FIGS. 1 and 2. Approximately 20-39 such glands are found in man. Infection in an anal gland may result in an abscess, which then tracks through or around the sphincter muscles into the perianal region, where it drains either spontaneously or surgically. The resulting tract is known as a fistula. The inner opening of the fistula, usually located at the dentate line, is known as the primary opening 2. The outer (external) opening, located in the perianal skin, is known as the secondary opening 3.
FIGS. 1 and 2 show examples of the various paths that an anorectal fistula may take. These paths vary in complexity. Fistulae that take a straight line path from the primary opening 2 to the secondary opening 3 are known as simple fistulae 4. Fistula that contain multiple tracts ramifying from the primary opening 2 and have multiple secondary openings 3 are known as complex fistulae 5.
The anatomic path that an anorectal fistula takes is classified according to its relationship to the anal sphincter muscles 6, 7. The anal sphincter includes two concentric bands of muscle—the inner, or internal, sphincter 6 and the outer, or external, anal sphincter 7. Fistulae which pass between the two concentric anal sphincters are known as inter-sphincteric fistulae 8. Those which pass through both internal 6 and external 7 sphincters are known as trans-sphincteric fistulae 9, and those which pass above both sphincters are called supra-sphincteric fistulae 10. Fistulae resulting from Crohn's disease usually ignore these anatomic paths, and are known as extra-anatomic fistulae.
Many complex fistulae contain multiple tracts, some blind-ending 11 and others leading to multiple secondary openings 3. One of the most common and complex types of fistulae are known as horseshoe fistulae 12, as illustrated in FIG. 2. In this instance, the infection starts in the anal gland (the primary opening 2) and two fistulae pass circumferentially around the anal canal, forming a characteristic horseshoe configuration 12.
Surgical treatment of fistulae traditionally involves passing a fistula probe through the tract, in a blind manner, using only tactile sensation and experience to guide the probe. Having passed the probe through the fistula tract, the overlying tissue is surgically divided. This is known as a surgical fistulotomy. Because a variable amount of sphincter muscle is divided during the procedure, fistulotomy may result in impaired sphincter control or even incontinence.
Alternatively, the fistula tract may be surgically drained by inserting a narrow diameter rubber drain, known as a seton, through the tract. After the seton is passed through the fistula tract, it may be tied as a loop around the contained tissue and left for several weeks or months. This procedure is usually performed to drain infection from the area and to mature the fistula tract prior to a definitive closure or sealing procedure.
More recently, methods have evolved to inject sclerosant or sealant (collagen or fibrin glue) into the tract of the fistula. Such sealants are described in Rhee, U.S. Pat. No. 5,752,974, for example. The main drawback with these methods is that the glues have a liquid consistency and tend to run out of the fistula tract once the patient becomes ambulatory. In addition, failure rates of these methods are high (up to 86% failure). See Buchanan et al., Efficacy of Fibrin Sealant in the Management of Complex Anal Fistula, DIS COLON AND RECTUM Vol. 46, No. 9, 46:1167-1174 (September 2003). Usually, multiple injections of glue are required to close the fistula. In some instances, closure of a fistula using a sealant may be performed as a two-stage procedure, comprising a first-stage seton placement, followed by injection of the fibrin glue several weeks later. This procedure reduces residual infection and allows the fistula tract to “mature” prior to injecting a sealant. Injecting sealant or sclerosant into an unprepared or infected fistula as a one-stage procedure may cause a flare-up of the infection and even further abscess formation. Alternative methods and instruments, such as coring-out instruments (See, e.g., U.S. Pat. Nos. 5,628,762 and 5,643,305), simply make the fistula wider and more difficult to close.
An additional means of closing the primary opening is by surgically creating a flap of skin, which is drawn across the opening and sutured in place. This procedure (the endo-anal flap procedure) closes the primary opening, but is technically difficult to perform, is painful for the patient, and is associated with a high fistula recurrence rate.
An important step in successful closure of a fistula is accurate identification and closure of the primary opening. An accurate means of identifying the primary opening involves endoscopic visualization of the fistula tract (fistuloscopy), as disclosed in co-pending application Ser. No. 10/945,634 (Armstrong). Once the primary opening has been accurately identified, effective closure is necessary to prevent recurrence. The current invention comprises a graft that may be used to effectively plug or occlude the primary opening of the fistula tract.